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SEMI MF1527-1104 © SEMI 2003, 2004 11 11.1.4 Operation of eddy current gage, spreading resistance probe, and m erc ur y probe, as required , including familiarity with appro priate standard test methods (see Section 10.1…

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SEMI MF1527-1104 © SEMI 2003, 2004 10
Section 7.2 (conversion from dopant density to
resistivity) of SEMI MF723, by solving the appropriate
equation given in this section for resistivity iteratively
for the net carrier density.
9.2.5 Provide the following information with the
reference wafer:
9.2.5.1 Wafer identification (including source crystal
and position therein, orientation, conductivity type, and
dopant impurity),
9.2.5.2 Date of calibration,
9.2.5.3 Calibrating laboratory and operator,
9.2.5.4 Identification of instrumentation used,
9.2.5.5 Nominal wafer diameter, in mm,
9.2.5.6 Average wafer thickness, in mm,
9.2.5.7 Total thickness variation over the 38-mm
diameter central circle, in m,
9.2.5.8 Method for determining thickness and
thickness variation,
9.2.5.9 Nominal measuring current, in mA,
9.2.5.10 Average center-point resistivity, corrected to
23°C, in ·cm,
9.2.5.11 Number of resistivity measurements (m) per
determination, and
9.2.5.12 Standard deviation of corrected center-point
resistivity values, in ·cm.
9.2.6 If appropriate for the application also provide any
or all of the following:
9.2.6.1 Net carrier density, in cm
3
,
9.2.6.2 Diameter of the area over which thickness and
radial resistivity uniformity were obtained, if different
from 38 mm,
9.2.6.3 Measures of macro-scale and micro-scale radial
sheet resistance (resistivity) uniformity, including the
method or methods by which the uniformity was
determined,
9.2.6.4 Measure of axial resistivity uniformity
estimate, including a description of the procedure by
which the estimate was obtained, and
9.2.6.5 Average voltage-current ratio, corrected to
23°C for a four-point probe with ideal (equal) 1.59-mm
probe-tip spacing.
10 Application of Resistivity Reference
Materials
10.1 Calibration procedures for various resistivity
measurement equipment are given in the applicable
resistivity test method as summarized in Table 2.
10.2 For control of instruments for routine resistivity
measurements, a control chart for individuals with
moving range should be employed. In general, single
measurement determinations of resistivity are made for
routine purposes; therefore, the control should be
carried out on this basis. Established procedures should
be used for generating and maintaining the individuals
and moving range control charts, for determining the
existence of out-of-control conditions, and taking the
appropriate corrective action. A suggested procedure is
given in Section R1-4 for use in organizations without
previously established procedures.
11 Operator Training Requirements
11.1 Personnel responsible for selection and calibration
of resistivity reference wafers should be skilled in the
following areas:
11.1.1 Operation of four-point probe resistivity
measurement apparatus, including familiarity with
SEMI MF84 or DIN 50431,
11.1.2 Sources of radial and longitudinal resistivity
variations in silicon crystal,
11.1.3 Operation of resistivity mapping apparatus,
manual or automatic, as appropriate,
Table 2 Summary of Test Methods Applicable to Resistivity and Related Measurements
Measurement Equipment Applicable Test Method(s)
In-line Four-point Probe SEMI MF84 or DIN 50431
Non-contact Eddy-current Gage SEMI MF673, DIN 50445 or DIN 50447
Spreading Resistance Probe SEMI MF525 or SEMI MF672
Mercury Probe SEMI MF1392, SEMI MF1393 or DIN 50439
Dual-configuration Four-point Probe SEMI MF1529
SEMI MF1527-1104 © SEMI 2003, 2004 11
11.1.4 Operation of eddy current gage, spreading
resistance probe, and mercury probe, as required,
including familiarity with appropriate standard test
methods (see Section 10.1),
11.1.5 Generation and maintenance of
X
and s control
charts for measurement equipment together with
recognition of out-of-control conditions and the
appropriate corrective action procedures,
11.1.6 Measurement of wafer thickness and TTV, and
11.1.7 Care and use of resistivity CRMs.
11.2 Individuals responsible for preparation of
resistivity reference wafers should have a good
understanding of wafer shaping processes, especially
slicing and lapping.
11.3 Operators and other personnel associated with the
use of resistivity reference wafers for calibration or
control of resistivity measurement equipment used in
production or for other routine measurements, should
be well trained in the use and maintenance of the
equipment as well as in meticulous record keeping;
accurate records are essential to the integrity of the
calibration and control procedures. Familiarity with
statistical process control procedures including
generation and maintenance of moving range control
charts, recognition of out-of-control conditions, and the
appropriate corrective action chain is also required.
12 Keywords
12.1 certified reference materials; control chart; eddy
current gage; four-point probe method; mercury probe;
reference materials; resistivity; resistivity reference
wafer; semiconductor; sheet resistance; silicon wafers;
SPC; spreading resistance probe; Standard Reference
Materials
SEMI MF1527-1104 © SEMI 2003, 2004 12
RELATED INFORMATION 1
PROCEDURES FOR DETERMINING THE PRESENCE OF OUT-OF-
CONTROL CONDITIONS AND THE NEED FOR CORRECTIVE ACTION
NOTICE: This related information is not an official part of SEMI MF1527. It was derived from
information developed during the original preparation of the standard in ASTM Committee F-1 in 1994.
This related information was approved for publication by full letter ballot procedures.
R1-1 Types of Control Charts
R1-1.1 Three types of control charts are employed for
various purposes in connection with the use of
resistivity reference wafers.
R1-1.2 Two
X
and s charts are used for the control of
primary resistivity measuring instruments. One of these
is the usual type of chart for which the control limits are
established from measurements made with the
instrument (see Section 7.1.1). The second, intended to
ensure traceability, differs from the usual control chart
in that it has limits that are based not on the
measurements themselves but instead on the
characteristics of the CRMs used for the measurements
(see Section 7.1.2). These two types of control charts
are of the types intended to provide control with no
standard given and control with respect to a given
standard, respectively.
10
R1-1.3 The third type of chart is one based on
individual measurements and the moving range, which
is the difference between one measurement and the
next. The control limits for this chart are based on the
measurements. This type of chart is used for control of
instruments for routine resistivity measurements (see
Section 10.2).
R1-2 Control Charts for Primary Resistivity
Measuring Instruments
R1-2.1 Since there is no standard given for these
charts, the limits are based on the initial series of
resistivity determinations. First, select an appropriate
number of measurements (six to ten) for the resistivity
determination, and make the same number of
measurements for each determination. Begin
construction of the instrument
X
and s charts by
making 25 to 30 center-point resistivity determinations
in accordance with the procedure of Section 7.1.1 on
one or more resistivity reference wafers covering the
resistivity range of the specimens to be measured. If no
other acceptable material is available, CRMs or other
commercially obtained calibrated wafers can be
employed until suitable reference wafers have been
10 Manual on Presentation of Data and Control Chart Analysis:
MNL 7, 6th Edition, (ASTM, West Conshohocken, PA, (1991) §3-3.
prepared. Measurements should be taken regularly,
every day or every shift, as appropriate. If variations
between operators are suspected, separate control charts
should be maintained by different operators.
R1-2.2 Record the date, time, sample identification,
operator, number of separate resistivity measurements
(six to ten), m; each resistivity value obtained, X
ij
; the
average of each group of m measurements,
;
i
X and the
sample standard deviation of each group, s
i
.
NOTE 1: The average and standard deviation of each group
of measurements are obtained as follows:


m
j
m
j
iijiiji
XX
m
sX
m
X
11
2
)(
1
1
and
1
R1-2.3 Construct
X
and s run charts of these data for
each wafer measured by plotting on separate graphs the
values of
X
and s in the order in which they were
obtained as shown in Figure R1-1.
R1-2.4
Calculate the grand averages,
X
and s of the
i
X and s
i
values, respectively, as follows:
n
i
i
n
i
i
s
n
sX
n
X
11
1
and
1
(R1-1)
where:
n = number of measurements (25 to 30, see Section
R1-2.1).
Take these grand averages as the central lines of the
X
and s control charts, respectively.
R1-2.5 Determine the upper and lower control limits
for the
X
control chart from the following equations:
11
sAXLCLsAXUCL
33
and (R1-2)
where:
UCL = upper control limit,
LCL = lower control limit, and
11 Manual on Presentation of Data and Control Chart Analysis:
MNL 7, 6th Edition, (ASTM, West Conshohocken, PA, (1991) §3-9,
Tables 5 and Tables 6.